Xenos
A Greek word which means "stranger" or "alien." "Xenophobia," or "fear of the strange," comes from this root.
In Warhammer 40,000
The Imperium of Man uses "xenos" as a catch-all term for any non-human life forms. For example, the Ordo Xenos is the branch of the Inquisition which deals with aliens, and they have whole litanies about what happens to Xenos they get their hands on, like "Mark of the Xenos" (also the name of a Rogue Trader sourcebook).